Optical disk, optical disk device, and method of reproducing information on optical disk

ABSTRACT

The present invention is aimed at providing an optical disk, an optical disk device, and an optical disk reproduction method, for allowing for stable and efficient reading of address information. The optical disk includes a plurality of tracks each divided into a plurality of recording sectors. Each of the recording sectors includes a header region. The header region includes address information for identifying the position of the corresponding recording sector and address synchronous information for identifying the recording position of the address information for bit synchronization. The address information has been modulated using a run length limit code of a maximum inversion interval of T max  bits (T max  is a natural number), and the address synchronous information includes two patterns of which inversion interval is (T max +3) bits or more, so that the reproduced signal of the address synchronous information is distinguished from the reproduced signal of other information.

This is a continuation of copending U.S. application Ser. No.09/117,825, filed Dec. 14, 1997which is a 371 of PCT/JP97/00337 filedFeb. 7, 1997.

TECHNICAL FIELD

The present invention relates to an optical disk, an optical diskdevice, and an optical disk reproduction method, forrecording/reproducing digital signals.

BACKGROUND ART

In recent years, optical disk devices have attracted attention as meansfor recording/reproducing a large capacity of data, and are under activetechnical developments for achieving higher recording density.

Presently prevailing rewritable optical disks include spiral-shapedgroove tracks composed of concave and convex portions (each having awidth of about 50%) formed on a surface of a disk substrate at a pitchof 1 to 1.6 μm. On the surface of the substrate, a thin film including arecording material (e.g., Ge, Sb, and Te in the case of a phase-changetype optical disk) as a component is formed by a method such assputtering. The disk substrate is fabricated in the following manner.First, a stamper is produced from a prototype where concave grooves andpits for sector addresses and the like are formed by cutting by lightbeam irradiation. Using such a stamper, the disk substrates made ofpolycarbonate and the like are mass-produced. The rewritable opticaldisks require sector-unit management for data recording andreproduction. Accordingly, at the fabrication of the disks, concave andconvex portions (pits) are often formed on a recording surface,simultaneously with the formation of guide grooves for tracking control,so as to record address information of each sector.

Each track of the optical disk with the above structure is irradiatedwith a light beam having a predetermined recording power, so as to formrecording marks on the recording thin film. The portions irradiated withthe light beam (the recording marks) have different opticalcharacteristics (reflection characteristics) from the other portions ofthe recording thin film. Thus, the recorded information can bereproduced by irradiating the track with a predetermined reproductionpower and detecting light reflected from the recording film.

In the following description, the pits of physical concave and convexportions and the recording marks obtained by a change in the opticalcharacteristics of the recording thin film are generically referred toas “marks”, unless otherwise specified. The pits are read-only marksonce formed, while the recording marks are rewritable. At thereproduction of recorded information, the two types of marks are read aschanges in the amplitude of reproduction signals. The concave and convexportions as used herein refers to the shapes as are viewed from areproduction beginning of the optical disk device. In other words, the“pits” refer to the convex portions as are viewed from the reproductionhead, and the “grooves” also refer to the convex portions.

Techniques for achieving an optical disk with a high recording densityinclude increasing the recording density in the track direction andincreasing the recording density in the linear velocity direction.

Increasing the recording density in the track direction includesreducing the distance between tracks (the track pitch). One techniquefor reducing the track pitch is land/groove recording where signals arerecorded both on convex tracks (groove portions) and concave tracks(land portions). The land/groove recording realizes double recordingdensity, compared with the case of recording signals on either thegroove porions or the land portions, if the other conditions are thesame.

One technique for increasing the recording density in the linearvelocity direction is referred to as mark length recording where bothends of a mark are made to correspond to “1” of modulation data. FIG. 1illustrates an example of the mark length recording in comparison withinter-mark recording. Referring to FIG. 1, a sequence Y representsdigital data modulated using a run length limit code. The run lengthlimit code as used herein refers to a code sequence where the number ofcontinuous “0”s interposed between every adjacent “1”s (hereinbelow,called the zero run) is limited to a predetermined number. The interval(length) from one “1” to the next “1” in the sequence Y is called aninversion interval. The limits, i.e., the minimum and maximum values ofthe inversion interval of the sequence Y are determined by thelimitation of the zero run. Such values are called the minimum inversioninterval and the maximum inversion interval.

When the sequence Y is recorded using the intermark recording (PPM; pitposition modulation), the “1” of the sequence Y corresponds to arecording mark 101, and the zero run corresponds to a space 102. Whenthe sequence Y is recorded using the mark length recording (PWM; pulsewidth modulation), the recording state, i.e., whether the recording mark101 or the space 102, is switched by the appearance of “1” in thesequence Y. When the mark length recording is employed, the inversioninterval corresponds to the length of the recording mark 101 or thespace 102.

When a run length limit code of which the minimum inversion interval is2 or more is used, the mark length recording may have an increasednumber of bits per unit length, compared with the inter-mark recording.For example, consider the case where the minimum value of the physicalsize of a mark which can be formed on a disk (called a mark unit) is thesame in both the mark length recording and the inter-mark recording. Asis observed from FIG. 1, while the inter-mark recording utilizes threemark units to record data of the minimum code length (three bits, “100”,in the sequence Y), the mark length recording utilizes only one markunit. For example, while the recording density in the inter-markrecording is approximately 0.8 to 1.0 μm/bit, the recording density inthe mark length recording is approximately 0.4 μm/bit.

In general, the tracks on the optical disk are divided into recordingsectors which represent minimum access units. Address information isprerecorded on each recording sector as described above. By reading theaddress information, the access to the recording sectors for datarecording/reproduction is possible.

FIG. 2A illustrates a signal format of each recording sector of arewritable optical disk which is in accordance with ISO (see ISO/IEC10090). A recording sector 103 begins with a header 104 where addressinginformation for reading address information is prerecorded by formingconcave and convex portions on the recording surface. A recording field105 stores user data where digital data is modulated using a (2,7)modulation code for the inter-mark recording. FIG. 3 shows a conversiontable of (2,7) modulation codes. As is observed from FIG. 3, by the(2,7) modulation, i-bit digital data (i - 2, 3, 4) is converted into a2xi-bit code sequence. The (2,7) modulation codes are run length limitcodes where the zero run is limited between 2 and 7.

FIG. 2B shows the construction of the header 104. A sector mark SM isprovided so that the optical disk device can identify the beginning ofthe recording sector without clock reproduction by a phase locked loop(PLL). As shown in FIG. 2C, the sector mark SM includes a pattern usingcomparatively long marks. Since the sector mark SM has thispredetermined pattern, and the amplitude of the reproduction signalsthereof is large, the sector mark SM is distinguishable from other datarecorded using the inter-mark recording. The position of the header 104is detected by detecting the sector mark SM, thereby to reproduce theaddress information.

VFO regions VFO1 and VFO2 shown in FIG. 2B are provided so that theoptical disk device can obtain bit synchronization of reproductionsignals using a clock reproduction by the PLL. A 2-zero run sequentialpattern is recorded using the inter-mark recording.

Address marks AM are provided so that the optical disk device canidentify the byte synchronization of subsequent address fields ID1, ID2,and ID3. Each of the address marks AM includes a pattern as shown inFIG. 2D recorded using the inter-mark recording technique. The patternof the address mark AM includes a pattern of T_(max)+1=9 bits whereT_(max) is a maximum inversion interval of the (2,7) modulation code(T_(max)=8). This pattern does not appear in data recorded by the (2,7)modulation code.

Each of the address fields ID1, ID2, and ID3 includes: addressinformation composed of track numbers, sector numbers, and the like; andcyclic redundancy check (CRC) codes for error detection during datareproduction, which are subjected to the (2,7) modulation and recordedusing the inter-mark recording.

A postamble PA is provided to indicate the end of the (2,7) modulateddata in the address field ID3.

FIG. 4 shows an example of signal amplitudes obtained when informationrecorded on the header 104 is reproduced by the optical disk device. Asis observed from FIG. 4, the amplitudes of the reproduced signals areproportional to the lengths of the corresponding marks. The amplitude ofthe reproduced signal of the sector mark SM which has a long length islarger than that of the reproduced signal of other data. This allows forthe identification of the sector mark SM by detecting the envelope ofthe reproduced signal waveform, and thus the detection of the beginningof each recording sector.

In the above example, all of the (2,7) modulated data is recorded usingthe inter-mark recording. However, in an optical disk having the header104, when data is recorded using the mark length recording for improvingthe recording density, the marks recorded in the address fields ID1 toID3 of the header 104 and the marks recorded in the recording field 105have a certain length determined by the zero run limitation of themodulation code. Accordingly, the amplitude of the reproduced signal ofdata recorded using the mark length recording becomes large, comparedwith that recorded using the inter-mark recording where each markcorresponds to the 1-bit long “1”. In the mark length recording,therefore, the difference in the signal amplitude (or the difference inthe pattern) between the sector mark SM and the other portions becomessmall compared with the case of the inter-mark recording. This makes itdifficult to detect the beginning of the recording sector 103 by theenvelope.

Moreover, when the above-described address mark AM is used, an erroneousdetection of the address mark AM due to an erroneous bit shift of “1”may occur. For example, a code sequence obtained by the (2,7) modulationof digital data { . . . 10110011 . . . } is converted into { . . .0100100000001000 . . . } from a conversion table such as that shown inFIG. 3. At this time, the pattern of the address mark AM is{0100100000000100} as shown in FIG. 2D. If “1” of the above (2,7)modulated pattern shifts by one bit, the resultant pattern is identicalto the address pattern AM,. which will cause erroneous detection.

In view of the foregoing, the objects of the present invention are toprovide an optical disk, an optical disk device, and an optical diskreproduction method, where address information can be read reliably evenwhen high recording density is achieved by employing mark lengthrecording and the like.

DISCLOSURE OF INVENTION

The optical disk of the present invention includes a plurality of trackseach divided into a plurality of recording sectors, each of therecording sectors including a header region, wherein the header region,includes address information for identifying a position of thecorresponding recording sector and address synchronous information foridentifying a recording position of the address information for bitsynchronization. The address information has been modulated using a runlength limit code of a maximum inversion interval of T_(max) bits(T_(max) is a natural number), and the address synchronous informationincludes two patterns of which inversion interval is (T_(max)+3) bits ormore, so that a reproduced signal of the address synchronous informationis distinguished from a reproduced signal of other information. With theabove construction, the above objects are attained.

In one embodiment, the address synchronous information includes a firstpattern and a second pattern which are different in either a physicalshape or an optical characteristic of a recording surface of the opticaldisk, and the address synchronous information includes one first patternhaving a length of (T_(max)+3) bits or more and one second patternhaving a length of (T_(max)+3) bits or more.

The pattern may be a convex portion (pit) formed physically on therecording surface of the optical disk, and the second pattern is aconcave portion formed physically on the recording surface of theoptical disk.

The first pattern may be a recording mark formed by changing areflection characteristic of the recording surface of the optical disk,and the second pattern is a space on the recording surface.

Preferably, a total bit length of the first pattern included in theaddress synchronous information and a total bit length of the secondpattern included in the address synchronous information are equal toeach other.

Preferably, the header region includes four-time repetition of theaddress information and the address synchronous information.

The optical disk of this invention includes a plurality of tracks eachdivided into a plurality of recording sectors, each of the recordingsectors including a header region, wherein the header region includesaddress information for identifying a position of the correspondingrecording sector, address synchronous information for identifying arecording position of the address information for bit synchronization,and clock synchronous information for reproducing a clock signal, theaddress information has been modulated using a run length limit code ofa minimum inversion interval of T_(min) bits and a maximum inversioninterval of T_(max) bits (T_(max) and T_(min) are natural numberssatisfying T_(max)>T_(min)), the clock synchronous information is asequential pattern of alternate repetition of d-bit long mark and space(d is a natural number satisfying T_(min)≦T_(max)), and the addresssynchronous information includes two patterns of which inversioninterval is (T_(max)+3) bits or more, so that a reproduced signal of theaddress synchronous information is distinguished from a reproducedsignal of other information. With the above construction, the aboveobjects are attained.

In one embodiment, each of the address synchronous information and theclock synchronous information includes a first pattern and a secondpattern which are different in either a physical shape or an opticalcharacteristic of a recording surface of the optical disk, and theaddress synchronous information includes one first pattern having alength of (T_(max)+3) bits or more and one second pattern having alength of (T_(max)+3) bits or more.

In another embodiment, the minimum inversion interval T_(min) is 3, themaximum inversion interval T_(max) is 11, and the value d is 3.

In still another embodiment, the minimum inversion interval T_(min) is3, the maximum inversion interval T_(max) is 11, and the value d is 4.

Preferably, the header region includes four-time repetition of the clocksynchronous information, the address information, and the addresssynchronous information.

The optical disk comprising a plurality of tracks each divided into aplurality of recording sectors, wherein each recording sector includes aheader region and a postamble region following an end of the headerregion, and the postamble region includes a pattern determined based ona modulation result of data of the header region. With aboveconstruction, the above objects are attained.

In one embodiment, the data on the header region is modulated using amodulation code for performing a conversion in a table based on a state,the postamble region includes information for identifying the state.

The information for identifying the state may be at least one specificbit having a predetermined value, and a bit located adjacent to thespecific bit has substantially the same value as the predetermined valueof the specific bit.

The optical disk of this invention includes a plurality of tracks eachdivided into a plurality of recording sectors, wherein each recordingsector includes a header region, a data recording region, and apostamble region following an end of the data recording region, and thepostamble region includes a pattern determined based on a modulationresult of data of the data recording region. With this construction, theabove objects are attained.

In one embodiment, the data on the data recording region is modulatedusing a modulation code for performing conversion in a table based on astate, the postamble region includes information for identifying thestate.

The information for identifying the state may be at least one specificbit having a predetermined value, and a bit located adjacent to thespecific bit has substantially the same value as the predetermined valueof the specific bit.

In one embodiment, the recording sector further includes a guard datarecording region following the postamble region for recording dummydata.

In another embodiment, the data recording region includes data modulatedusing a run length limit code of a minimum inversion interval of T_(min)bits and a maximum inversion interval of T_(max) bits (T_(max) andT_(min) are natural numbers satisfying T_(max)>T_(min)), and the guarddata recording region includes a pattern of alternate repetition of ak-bit long optical mark and a k-bit long optical space (k is a naturalnumber satisfying T_(min)≦k≦T_(max)).

The optical disk of this invention includes a plurality of tracks eachdivided into a plurality of recording sectors, wherein each recordingsector includes a header region, and the header region includes anaddress region having a postamble region at an end of the addressregion, and the postamble region has a pattern which ends with non-pitdata or a space. With this construction, the above objects are attained.

The header region may include a plurality of the address regions.

The address regions may be located in the middle of groove portions andland portions of the tracks.

The optical disk of this invention includes a plurality of tracks eachdivided into a plurality of recording sectors, wherein each recordingsector includes a header region, the header region includes a pluralityof address regions, each of the address regions includes a VFO region ata beginning of the address region, and the VFO region has a patternwhich starts with non-pit data or a space. With this construction, theabove objects are attained.

In one embodiment, the address region includes an address informationregion where address information is recorded by a mark length recordingfor identifying a position of the corresponding recording sector, andthe address information is modulated using a run length limit code of aminimum inversion interval of T_(min) bits and a maximum inversioninterval of T_(max) bits (T_(max) and T_(min) are natural numberssatisfying T_(max)>T_(min)), and non-pit data or a space having a lengthin a range of T_(min) bits or more and T_(max) bits or less is providedbetween the address regions.

The address regions may be located in the middle of groove portions andland portions of the tracks.

The optical disk device of this invention is for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the devicecomprising: means for reading a reproduced signal from the optical disk;address reproduction means for obtaining the address information fromthe reproduced signal; detection means for detecting the sequentialpattern of the clock synchronous information from the reproduced signalto output a detection signal; and address reproduction permit means forpermitting the address reproduction means to perform a read operation ofthe address information based on the detection signal. With thisconstruction, the above objects are attained.

In one embodiment, the optical disk device further includes: clockgeneration means for generating a clock signal from the reproducedsignal; and clock reproduction permit signal for permitting the clockgeneration means to perform an operation of generating the clock signalbased on the detection signal.

The detection means may includes: binary means for converting thereproduced signal into binary data to output the binary data; samplingmeans for sampling the binary data at a predetermined frequency tooutput digital data; parallel conversion means for converting thedigital data into parallel data of at least m×n bits (m and n arenatural numbers); and a detection table for detecting a predeterminedsequence composed of n-time repetition of an m-bit pattern from theparallel data.

The optical disk device of this invention is for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the devicecomprising: means for reading a reproduced signal from the optical disk;clock generation means for generating a clock signal from the reproducedsignal; detection means for detecting the sequential pattern of theclock synchronous information from the reproduced signal to output adetection signal; and clock reproduction permit means for permitting theclock generation means to perform an operation of generating the clocksignal based on the detection signal.

In one embodiment, the detection means comprises: binary means forconverting the reproduced signal into binary data to output the binarydata; sampling means for sampling the binary data at a predeterminedfrequency to output digital data; parallel conversion means forconverting the digital data into parallel data of at least m×n bits (mand n are natural numbers); and a detection table for detecting apredetermined sequence composed of n-time repetition of an m-bit patternfrom the parallel data.

The reproduction method of this invention is for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the methodcomprising the steps of: retrieving a reproduced signal from the opticaldisk; detecting the sequential pattern of the clock synchronousinformation from the reproduced signal; permitting reading of theaddress information if the sequential pattern is detected; reading theaddress information from the reproduced signal in response to thepermission; and terminating the step of reading the address informationin a predetermined time period after the permission to return to thestep of detecting the sequential pattern. With this construction, theabove objects are attained.

In one embodiment, the reproduction method further includes the stepsof: permitting reproduction of a clock signal if the sequential patternis detected; and reproducing the clock signal from the reproduced signalin response to the permission.

The reproduction method of this invention is for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the methodcomprising the steps of: retrieving a reproduced signal from the opticaldisk; detecting the sequential pattern of the clock synchronousinformation from the reproduced signal; permitting reproduction of aclock signal if the sequential pattern is detected; and reproducing theclock signal from the reproduced signal in response to the permission.With this construction, the above objects are attained.

The reproduction method of this invention is for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the methodcomprising the steps of: retrieving a reproduced signal from the opticaldisk; determining a reproduction mode whether the reproduction mode isan initial mode during a time period from switching-on of the device ora track jump until the address information is first read from thereproduced signal or a normal mode during a time period from the readingof the address information until a next track jump is generated;detecting the sequential pattern of the clock synchronous informationfrom the reproduced signal; permitting reading of the addressinformation if the sequential pattern is detected in the initial mode asa first permitting step; reading the address information from thereproduced signal in response to the permission; generating a sectorpulse if the address information is correctly read; permitting readingof the address information from the reproduced signal based on thesector pulse in the normal mode as a second permitting step; andterminating the reading of the address information to return to the stepof determining a reproduction mode if the address information fails tobe read within a predetermined time period after either the first orsecond permission step. With this construction, the above objects areattained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view for explaining the mark length recording and theinter-mark recording.

FIG. 2A is a view illustrating a signal format of a recording sector ofa conventional optical disk.

FIG. 2B is a view illustrating a header of the conventional opticaldisk.

FIG. 2C is a view illustrating a recording pattern of a sector mark ofthe conventional optical disk.

FIG. 2D is a view illustrating a recording pattern of an address mark ofthe conventional optical disk.

FIG. 3 illustrates a modulation table of (2,7) modulation codes.

FIG. 4 is a view illustrating an example of reproduced signal waveformsat the header of the conventional optical disk.

FIGS. 5A to 5C are views for explaining a construction of an opticaldisk of one example according to the present invention.

FIG. 6 is a view illustrating an exemplary recording pattern of a VFOregion of the optical disk of the example according to the presentinvention.

FIGS. 7A to 7C are views illustrating exemplary recording patterns of anaddress mark of the optical disk of the example according to the presentinvention.

FIGS. 8A to 8D are views illustrating exemplary recording patterns ofthe address mark of the optical disk of the example according to thepresent invention.

FIG. 9 is a view illustrating an exemplary recording pattern of theaddress mark of the optical disk of the example according to the presentinvention.

FIG. 10 is a block diagram of an optical disk device of one exampleaccording to the present invention.

FIG. 11 is a block diagram of an exemplary inner construction of areproduction system shown in FIG. 10.

FIG. 12A is a block diagram of an exemplary inner construction of a VFOdetection circuit of the example according to the present invention.

FIG. 12B is a view illustrating the construction of a VFO detectiontable in the example according to the present invention.

FIG. 13 is a timing chart of exemplary waveforms of various signals usedin the optical disk device of the example according to the presentinvention.

FIG. 14 is a timing chart of exemplary waveforms of various signals usedin the optical disk device of the example according to the presentinvention.

FIG. 15 is a flowchart of an exemplary process after the turning-on of asystem control of the optical disk device of the example according tothe present invention.

FIG. 16 is a flowchart of an exemplary process of the system control ofthe optical disk device of the example according to the presentinvention.

FIG. 17A is a view illustrating a signal format of a recording sector ofan optical disk of another example according to the present invention.

FIG. 17B is a view illustrating a signal format of a header region ofthe optical disk of the example according to the present invention.

FIG. 18A is a block diagram of a modulation circuit for a statemodulation code in the example according to the present invention.

FIG. 18B is a view illustrating an exemplary content of a conversiontable shown in FIG. 18A.

FIG. 18C is a block diagram of the construction of a demodulationcircuit for the state modulation code in the example according to thepresent invention.

FIGS. 19A and 19B are views illustrating exemplary recording patternsfor a postamble in the example according to the present invention.

FIGS. 20A to 20C are views for explaining the construction of an opticaldisk of still another example according to the present invention.

FIGS. 21A and 21B are schematic views illustrating exemplaryarrangements of an address region of a header region of the optical diskof the example according to the present invention.

FIG. 21C is a view illustrating a coupling portion of address regionsshown in FIGS. 21A and 21B.

FIG. 22A is a schematic view illustrating the case where the couplingportion of the address regions of the optical disk includes marks andthe marks are ideally formed.

FIG. 22B is a schematic view illustrating the marks formed on thecoupling portion of the address regions of the optical disk.

FIGS. 23A and 23B are views illustrating the operation where an opticalspot performs data reproduction along a land track.

FIGS. 24A to 24H are views illustrating exemplary patterns of apostamble.

FIG. 25A is a view illustrating a signal format of a recording sector ofan optical disk of still another example according to the presentinvention.

FIG. 25B is a view illustrating an exemplary pattern recorded on a guarddata recording region in the example according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, the present invention will be described by way of examplewith reference to the relevant drawings.

(EXAMPLE 1)

FIG. 5A schematically illustrates an optical disk 1 a of the firstexample according to the present invention. As shown in FIG. 5A, theoptical disk 1 a has tracks 1 b formed in a spiral shape. Each track 1 bis divided into recording sectors 1 c in accordance with a predeterminedphysical format. As shown in FIG. 5A, the recording sectors 1 c aresequentially arranged in the circumferential direction to form the track1 b.

FIG. 5B illustrates a format of each recording sector 1 c of the opticaldisk 1 a of the first example according to the present invention.Referring to FIG. 5B, the recording sector 1 c starts with a headerregion 2 where addressing information for reading address information isprerecorded. A gap region 3, a data recording region 4, and a bufferregion 5 respectively follow the header region 2 in this order. The gapregion 3 has no data recorded thereon, but is used for power control ofa semiconductor laser used for data recording/reproduction and the like.The data recording region 4 is used to record user data. Redundant datasuch as an error correction code is added to the user data, to formdigital data. The digital data is modulated using a run length limitcode where the zero run is limited to the range of 2 to 10. Themodulated data is recorded on the data recording region 4 using the marklength recording. Such a run length limit code is called the (2,10)modulation code. The buffer region 5 is provided to absorb a rotationalfluctuation of the optical disk and the like. In the header region 2,information may be recorded as pits in a concave and convex shape on therecording surface, or as marks optically recorded in substantially thesame manner as that used in the recording on the data recording region.

As shown in FIG. 5C, the header region 2 is divided into four addressregions 6 a, 6 b, 6 c, and 6 d. Each of the address regions includes aVFO region, an address mark AM, and an address information region ID.For example, the address region 6 a includes a VFO region VF01, anaddress mark AM, and an address information region ID1, while theaddress region 6 b includes a VFO region VF02, an address mark AM, andan address information region ID2.

In the conventional header 104 shown in FIG. 2B, the sector mark SMprecedes the pattern composed of the VFO region, the address mark AM,and the address field ID which is repeated three times. In this example,no sector mark is recorded on each header region 2, but the addressregion, similar to the above pattern, which is composed of the VFOregion, the address mark AM, and the address information region ID, isrepeated four times.

The VFO regions VF01, VF02, VF03, and VF04 are used so that an opticaldisk device can obtain clock reproduction from reproduced signals. Asshown in FIG. 6, each VFO region has such a sequential pattern thatincludes 4-bit long marks and 4-bit long spaces appearing alternately.Each of the VFO regions may have the same length or different lengths.For example, if the VFO region VF01 is made longer than the other VFOregions VF02, VF03, and VF04, stable clock reproduction is obtained atthe beginning of the header region 2.

Each address mark AM is provided so that the optical disk device canidentify the position of the subsequent address information region ID toobtain bit synchronization therewith. FIG. 7A shows an example of theaddress mark AM of this example. As shown in FIG. 7A, marks are recordedon the optical disk using the mark length recording in accordance withthe signal sequence (bit pattern) of the address mark AM. The resultantsignal to be read has an amplitude in accordance with the pattern ofmarks and spaces (portions other than the marks). In this example, theaddress mark AM has a pattern which includes one 14-bit long mark andone 14-bit long space. The address information regions ID1, ID2, ID3,and ID4 are representatively denoted as an address information regionID.

With respect to the address information region ID, digital data composedof data including address information such as the track number and thesector number and a predetermined error detection code added thereto arerecorded using the mark length recording, after the digital data aremodulated using a (2,10) modulation code.

Since the maximum inversion interval of the (2,10) modulation code is11, no marks or spaces having a length of 12 bits or more are includedin the pattern in any of the address information regions ID and the datarecording regions. Even if the 11-bit long mark in the addressinformation region ID or the data recording region is erroneouslyreproduced as a 12-bit long mark due to an edge shift of the mark or thelike, and furthermore the 14-bit long mark in the address mark AM iserroneously reproduced as a 13-bit long mark, the one-bit longdifference still exists therebetween. Accordingly, unless the mark/spacein either one of the regions is subjected to an edge shift by 2 or morebits, a failure to detect the 14-bit long mark in the address mark AM oran erroneous detection of a pattern in the address information region IDor the data recording region as a 14-bit long mark will not occur. Inthis way, the address mark AM can be detected without fail by recordingtwo patterns (one mark and one space) having a length of T_(max)+3 bitsor more where T_(max) is the maximum inversion interval.

As described above, the address mark AM includes two 14-bit longmark/spaces. This pattern reduces the probability of erroneous detectioncompared with a pattern including only one 14-bit long mark or space.Moreover, the pattern including only one 14-bit long mark or space canbe used as a data synchronization detection pattern for the datarecording region 4. This makes it possible, not only to maintain thereliability of the data synchronization detection, but also tofacilitate prevention of the data synchronization detection pattern frombeing erroneously detected as the address mark AM.

FIGS. 7B and 7C illustrate other examples of the address mark AM. Apattern including two 14-bit long marks as shown in FIG. 7B and apattern including two 14-bit long spaces as shown in FIG. 7C may be usedas the address mark AM. Using the patterns as shown in FIGS. 7B and 7C,however, the entire recording pattern may be made one-sided in thebalance of marks and spaces. If the entire recording pattern becomesone-sided, the low-frequency component of the pattern increases. Theincrease of the low-frequency components of the pattern varies theamount of the reproduced signal components in the servo frequency band,which affects the servo system. Accordingly, the amount of thelow-frequency component of the pattern should preferably be as small aspossible. Thus, the pattern as shown in FIG. 7A is preferable where theappearance of the marks and the spaces is balanced.

FIGS. 8A to 8D illustrate yet other examples of the address mark AM. Theaddress mark AM shown in FIG. 8A has a pattern composed of (6-bit longmark, 14-bit long space, 4-bit long mark, 4-bit long space, 14-bit longmark, 6-bit long space). The address mark AM shown in FIG. 8B has apattern composed of {4-bit long mark, 14-bit long space, 6-bit longmark, 6-bit long space, 14-bit long mark, 4-bit long space}. The addressmark AM shown in FIG. 8C has a pattern composed of (5-bit long mark,14-bit long space, 5-bit long mark, 5-bit long space, 14-bit long mark,5-bit long space). The address mark AM shown in FIG. 8D has a patterncomposed of (4-bit long mark, 14-bit long space, 4-bit long mark, 4-bitlong space, 14-bit long mark, 4-bit long space).

In all of the above patterns, the total number of bits of the marks andthe total number of bits of the spaces are equal to each other. Thus,these patterns include two 14-bit long mark/spaces and also include areduced amount of low-frequency components.

In the patterns shown in FIGS. 8A to 8D, the number of mark/spaceinversions is large compared with the patterns shown in FIGS. 7A to 7C.As the number of mark/space inversions increases, edge information inincreases and thus the error due to a bit shift occurs less easily. Inother words, the patterns shown in FIGS. 8A to 8D have a smallerprobability of causing erroneous synchronization detection due to a bitshift than the patterns shown in FIGS. 7A to 7C.

In some cases, the processing of a modulation circuit, a demodulationcircuit, and the like becomes simpler if the address mark AM has alength of an integer number of data bytes. FIG. 9 illustrates a patternof the address mark AM obtained by using a modulation code whichmodulates one data byte into 16 bits. The address mark AM is 48-bitlong, i.e., 3-data byte long. The pattern is composed of (4-bit longspace, 4-bit long mark, 14-bit long space, 4-bit long mark, 4-bit longspace, 14-bit long mark, 4-bit long space).

The pattern of the address mark AM shown in FIG. 9 includes a largernumber of mark/space inversions than the pattern shown in FIG. 7A. Asthe number of mark/space inversions increases, edge informationincreases and thus the error due to a bit shift occurs less easily asdescribed above. In other words, the pattern shown in FIG. 9 has asmaller probability of causing erroneous synchronization detection dueto a bit shift than the pattern shown in FIG. 7A.

FIG. 10 is a block diagram of an optical disk device 100 forrecording/reproducing data on/from the optical disk 1 a having thesignal format described above. Referring to FIG. 10, the optical diskdevice 100 includes a spindle motor 7, a head 8, a preamplifier 9, amodulation circuit 11, a laser driving circuit 14, a reproduction system16, a system control 18, and a servo system 50.

The spindle motor 7 rotates the optical disk 1 a at a predeterminednumber of revolutions. The head 8 incorporates a semiconductor laser, anoptical system, an optical detector, and the like therein though thesecomponents are not shown. Laser light emitted by the semiconductor laseris converged by the optical system so that a light spot having apredetermined power for recording or reproduction is formed on arecording surface of the optical disk 1 a to realize datarecording/reproduction. Reflected light from the recording surface isconverged by the optical system and converted into a current by theoptical detector. The signal current output from the head 8 is furtherconverted into a voltage and amplified by the preamplifier 9, so as tobe output as a reproduced signal 10.

The servo system 50 performs the rotational control of the spindle motor7, the phase control for moving the head 8 in the radial direction ofthe optical disk1 a, the focusing control for focusing the light spot onthe recording surface of the optical disk1 a, and the tracking controlfor tracking the light spot along the center of the track.

The modulation circuit 11 performs the (2,10) modulation for input data12, and outputs modulated data 13 to the laser driving circuit 14.During the reproduction, the laser driving circuit 14 outputs a laserdriving signal 15 for driving the semiconductor laser incorporated inthe head 8 to emit light with the power for reproduction. During therecording, the laser driving circuit 14 outputs the laser driving signal15 for driving the semiconductor laser to emit light with the power forrecording so that the mark length recording is performed on the datarecording region 4 in accordance with the supplied modulated data 13.

The reproduction system 16 reproduces various data recorded on theheader region 2 and the data recording region 4 from the reproducedsignal 10 supplied from the preamplifier 9, and outputs the data asreproduced data 17.

The system control 18 controls the operations of the modulation circuit11, the laser driving circuit 14, the reproduction system 16, and theservo system 50 based on the reproduced data 17 reproduced by thereproduction system 16 and a user's configuration 19.

FIG. 11 is a block diagram illustrating an example of the internalconstruction of the reproduction system 16. Hereinbelow, the method forreproducing address information 40 recorded on the header region 2 fromthe reproduced signal 10 will be described. As shown in FIG. 11, thereproduction system 16 includes a clock reproduction circuit 20, abinary circuit 21, a VFO detection circuit 25, a reproduction permitcircuit 32, an address demodulation circuit 30, and a data demodulationcircuit 39.

The reproduced signal 10 received from the preamplifier 9 is input intothe clock reproduction circuit 20 and the binary circuit 21. The clockreproduction circuit 20 includes a PLL for generating a reproductionclock 22 synchronized with the reproduced signal 10 in frequency andphase. The binary circuit 21 equalizes the waveform of the reproducedsignal 10 as required, to convert the signal into a binary patterncomposed of “1” and “0”. The binary circuit 21 outputs the convertedpattern itself to the VFO detection circuit 25 as asynchronous binarydata 23, and simultaneously synchronizes the converted binary patternwith the reproduction clock 22 supplied from the clock reproductioncircuit 20 to output as synchronous binary data 24. The synchronousbinary data 24 is supplied to the address demodulation circuit 30 andthe data demodulation circuit 39.

The VFO detection circuit 25 detects the sequential patterns recorded onthe VFO regions VF01, VF02, VF03, and VF04 based on the asynchronousbinary data 23, and outputs a VFO detection pulse 26 if predeterminedsequential patterns are detected.

FIG. 12A illustrates an example of the internal construction of the VFOdetection circuit 25. As shown in FIG. 12A, the VFO detection circuit 25includes a parallel conversion circuit 28, an oscillator 41, and a VFOdetection table 42. The parallel conversion circuit 28 receives theasynchronous binary data 23 and a fixed clock 27 generated by theoscillator 41. The parallel conversion circuit 28 latches theasynchronous binary data 23 at the timing of the fixed clock 27 andconverts the asynchronous binary data 23 into parallel data 29corresponding to continuous 32 clocks. The converted parallel data 29 isinput into the VFO detection table 42.

The VFO detection table 42 is, for example, composed of a table as shownin FIG. 12B which provides one-bit output from 32-bit input. The VFOdetection table 42 outputs the VFO detection pulse 26 of “1” if theparallel data 29 sequentially input at the timing of the fixed clock 27is a pattern composed of four-time repetition of an 8-bit pattern,{11110000} or {00001111}, or a pattern similar to this pattern.Otherwise, the VFO detection pulse 26 is “0”.

The first two lines of patterns in the VFO detection table shown in FIG.12B are detection patterns which are obtained when the frequency of thefixed clock 27 is substantially equal to the frequency of thereproduction clock and completely match with the 4-bit long mark/spacerepetition pattern, i.e., the recording pattern of the VFO region. Theother patterns in the third and subsequent lines are more or lessdifferent from the recording pattern of the VFO region. These patternsare provided so that patterns can be detected even in the case where theamplitude of the reproduced signal 10 varies or in the case where thefrequency of the fixed clock 27 and the frequency of the reproductionclock become more or less different from each other due to a rotationalfluctuation of the optical disk 1 a.

By using the VFO detection circuit 25 with the above internalconstruction, the-signals recorded on the VFO region can be detectedwith the fixed clock 27 corresponding to the frequency of a clockreproduced when the optical disk 1 a is rotating at a predeterminednumber of revolutions.

In this example, the parallel data 29 corresponding to 32 clocks areused for the detection of four periods of the 4-bit long mark/spacepattern. The number of bits of the parallel data 29 is not limited tothis number. An optimal number of bits may be selected so that anerroneous detection and an omission of detection are minimized. Thefrequency of the fixed clock 27 is not limited to the above-mentionedvalue. For example, if the frequency of the fixed clock is made tocorrespond to a quarter of the frequency of the reproduction clock, thepattern, {10101010} or {01010101} can be detected as the VFO pattern.

The VFO detection circuit 25 is not limited to the circuit having theinternal construction shown in FIG. 12A. For example, since thesequential pattern includes a specific frequency component, such aspecific frequency component may be detected directly from thereproduced signal 10 to detect the sequential pattern.

The address demodulation circuit 30 detects the address mark AM usingthe synchronous binary data 24 and the reproduction clock 22, performsthe (2,10) demodulation for the modulated data recorded on thesubsequent address information regions ID1, ID2, ID3, and ID4, anddetects an error in the demodulated data.

In this example, as described above, each header region 2 is composed offour repeated address regions each including the VFO region, the addressmark AM, and the address information region ID. Accordingly, whenaddress information is successfully reproduced without an error from twoor more address information regions among the four address informationregions ID1, ID2, ID3, and ID4, the reproduced values are output to thesystem control 18 as the address information 40. The addressdemodulation circuit 30 also outputs a sector synchronization pulse 31simultaneously with the output of the address information 40.

The four repeated recordings on the address regions will now bedescribed. The error rate for one address is about 10⁻². Assuming thatthe address information is obtained (the address is readable) when atleast two address regions among the four address regions aresuccessfully reproduced, the probability of failing to obtain theaddress information is as follows.

₄ C ₃ ×(10⁻²)³×(1−10⁻²)+(10⁻²)⁴≈4×10⁻⁶

wherein “₄C₃” is the number of combinations of three from four. Sinceone optical disk includes about 10⁶ recording sectors, the number ofrecording sectors in which an address is not readable in one opticaldisk is 10⁶×(4×10⁶)=4, which is within an allowable range. Thus, in thisexample, the number of recording sectors in which addresses are notreadable is substantially reduced to less than 10. This facilitates theidentification of each recording with an extremely high probability. Asa result, each recording sector can be identified by reliably retrievingthe address information from the address regions of the header of eachrecording sector, without the necessity of providing a sector mark SMfor identifying the header at the start of the header.

For comparison, the conventional header 104 (FIG. 2B) including threeaddress regions will be described. Assuming that the address is readable(the address information is obtained) when at least two address regionsamong the three address regions are successfully reproduced, theprobability of failing to obtain the address information is as follows.

₃ C ₂×(10⁻²)²×(1−10⁻²)+(10⁻²)³≈3×10⁻⁴

wherein “₃C₂” is the number of combinations of two from three. Since oneoptical disk includes about 10⁶ recording sectors, the number ofrecording sectors in which an address is not readable in one opticaldisk is 10⁶×(3×10⁴)=300, which is too large to be allowable.

Returning to FIG. 11, the reproduction permit circuit 32 generates aclock reproduction permit signal 34 based on the VFO detection pulse 26supplied from the VFO detection circuit 25 and a reproduction gatesignal 33 supplied from the system control 18, and outputs the signal tothe clock reproduction circuit 20. The clock reproduction circuit 20generates the reproduction clock 22 by synchronizing the incorporatedPLL with the phase of the reproduced signal 10 and outputs thereproduction clock to the binary circuit 21 only when the input clockreproduction permit signal 34 is “1”.

The reproduction permit circuit 32 also generates an addressreproduction permit signal 36 based on the VFO detection pulse 26 and anaddress gate signal 35 from the system control 18, and outputs thesignal to the address demodulation circuit 30. The address demodulationcircuit 30 detects the address mark AM by identifying the pattern of theaddress mark AM in the above-described manner only when the inputaddress reproduction permit signal 36 is “1”.

The reproduction permit circuit 32 further generates a data reproductionpermit signal 38 based on the VFO detection pulse 26 and a data gatesignal 37 from the system control 18, and outputs the signal to the datademodulation circuit 39. The data demodulation circuit 39 demodulatesrecorded data read from the data recording region 4 among thesynchronous binary data 24 and outputs the reproduced data 17 only whenthe input data reproduction permit signal 38 is “1”.

The system control 18 outputs the reproduction gate signal 33, theaddress gate signal 35, and the data gate signal 37 at a timing inaccordance with the information format shown in FIGS. 5B and 5C (i.e.,the reproduced signal format) using the sector synchronization pulse 31supplied from the address demodulation circuit 30 of the reproductionsystem 16 as the reference. These signals are supplied to thereproduction permit circuit 32 of the reproduction system 16 asdescribed above (FIG. 11).

FIG. 13 illustrates exemplary waveforms of the sector synchronizationpulse 31, the reproduction gate signal 33, the address gate signal 35,and the data gate signal 37 to show the relationship between thesesignals.

Referring to FIG. 13, the reproduced signal format conforms to theinformation recording format shown in FIG. 5B. The header region 2, thegap region 3, and the data recording region 4 of a recording sector 1Aare called a header region 2 a, a gap region 3 a, and a data recordingregion 4 a. Likewise, the header region 2, the gap region 3, and thedata recording region 4 of a recording sector 1B following the recordingsector 1A are called a header region 2 b, a gap region 3 b, and a datarecording region 4 b.

In the recording sector 1A, when the address information is correctlyreproduced from the header region 2 a, the sector synchronization pulse31 becomes “1” (high level) somewhere in the range from the end of theheader region 2 a through the gap region 3 a. The reproduction gatesignal 33 becomes “1” over the range at least covering the datarecording region 4 a of the recording section 1A and the header region 2b of the next recording sector 1B. The address gate signal 35 becomes“1” over the range at least covering the header region 2 b of the nextrecording sector 1B. The data gate signal 37 becomes “1” over the rangesubstantially covering the data recording region 4 a of the recordingsector 1A.

The system control 18 may be constructed so as to first examine thecontents of the address information 40 together with the sectorsynchronization pulse 31 and determine whether or not the recordingsectors 1A and 1B have address information to be recorded or reproducedbefore setting the respective gate signals to “1” in accordance with thetiming described above.

FIG. 14 illustrates exemplary waveforms of the VFO detection pulse 26,the sector synchronization pulse 31, the reproduction gate signal 33,the clock reproduction permit signal 34, the address gate signal 35, theaddress reproduction permit signal 36, the data gate signal 37, and thedata reproduction permit signal 38, shown in correspondence with thesignal format.

Referring to FIG. 14, it is assumed that an information address is firstcorrectly reproduced from the recording sector 1A and that the datarecording regions 4 a and 4 b of the recording sectors 1A and 1B have nodata recorded thereon but a data recording region 4 c of a nextrecording sector 1C has data thereon. Also assumed is that the beginningof the data recording region 4 c includes a sequential patternsubstantially equal to that on the VFO region, which is composed of4-bit long marks and spaces appearing alternately.

The clock reproduction permit signal 34 is “1” for a predetermined timeperiod after the VFO detection pulse 26 of “1” appears. The clockreproduction permit signal 34 is also “1” over the time period when thereproduction gate signal 33 is “1”. The above predetermined time periodis at least equal to the time period required to read the address marksAM and the address information regions ID1, ID2, ID3, and ID4 of theheader region 2. As a result, when the VFO detection pulse 26 becomes“1” for the respective VFO regions of the recording sector 1A, the clockreproduction permit signal 34 remains “1” until at least the end of theheader region 2 a. When the address information has been correctlyreproduced in the recording sector 1A and the sector synchronizationpulse 31 is output, the clock reproduction permit signal 34 becomes “1”for the header region 2 b of the next recording sector 1B without fail.Likewise, when the address information has been correctly reproduced inthe recording sector 1B and the sector synchronization pulse 31 isoutput, the clock reproduction permit signal 34 becomes “1” for theheader region 2 c of the next recording sector 1C without fail.

The address reproduction permit signal 36 is “1” for a predeterminedtime period after the VFO detection pulse 26 becomes “1 ” and for a timeperiod when the address gate signal 35 is “1”. The above predeterminedtime period is set to at least equal to the total time period requiredto read information from the address marks AM and the addressinformation regions ID1, ID2, ID3, and ID4. As a result, when the VFOdetection pulse becomes “1” for the respective VFO regions of therecording sector 1A, the address reproduction permit signal 36 remains“1” until at least the end of the header region 2 a. When the addressinformation has been correctly reproduced in the recording sector 1A andthe sector synchronization pulse 31 is output, the address reproductionpermit signal 36 becomes “1” for the header region 2 b of the nextrecording sector 1B without fail. Likewise, when the address informationhas been correctly reproduced in the recording sector 1B and the sectorsynchronization pulse 31 is output, the address reproduction permitsignal 36 becomes “1” for the header region 2 c of the next recordingsector 1C without fail.

The data reproduction permit signal 38 becomes “1” if the data gatesignal 37 is “1” when the VFO detection pulse 26 rises to “1I”, andremains “1” until the data gate signal 37 becomes “0”. The datareproduction permit signal 38 remains “0” if the data gate signal 37 is“0” when the VFO detection pulse 26 rises to “1”. As a result, since theVFO detection pulse 26 does not become “1” for the date recordingregions 4 a and 4 b where no data has been recorded, the datareproduction permit signal 38 remains “0”. For the data recording region4 c where data has been recorded, the VFO detection pulse becomes “1 ”at the header portion thereof. Accordingly, the data reproduction permitsignal 38 becomes “ 1” at a predetermined timing.

Thus, by using the VFO detection circuit 25 and the reproduction permitcircuit 32, the clock reproduction and the reproduction of the addressinformation are permitted in the header region 2 so that the clocksignal and the address information can be read. As described above, thesector synchronization pulse 31 is output after the address informationis reproduced from the header region 2 (see FIG. 13). According to thepresent invention, therefore, the address information of the recordingsector can be read even in the state where the time reference by thesector synchronization pulse 31 is not available.

Also, by using the system control 18, the address demodulation circuit30, and the reproduction permit circuit 32, once address information hasbeen reproduced from one recording sector (e.g., the recording sector1A) without an error, the clock reproduction and the reproduction of theaddress information in the header region 2 is permitted for therecording sector 1A and the next recording sector 1B, and the clockreproduction and the reproduction of the data in the corresponding datarecording regions 4 are permitted. Accordingly, once address informationhas been reproduced from one recording sector, the address informationand the data can be read in a more secured manner using the sectorsynchronization pulse 31 as the reference.

In the above example, the system control 18 generates three types ofgate signals using the sector synchronization pulse 31, while thereproduction permit circuit 32 generates three types of permit signalsusing the VFO detection pulse 26 and the three types of gate signals.Alternatively, the system control 18 may have the function of thereproduction permit circuit 32 so that the system control 18 candirectly generate the three types of permit signals.

FIG. 15 is a flowchart showing an example of a process performed when,after the switching-on of the optical disk device 100 (FIG. 10), thesystem control 18 outputs the clock reproduction permit signal 34 andthe address reproduction permit signal 36 using the VFO detection pulse26 and the sector synchronization pulse 31.

When the optical disk device 100 is switched on, the system control 18first performs a boosting processing (step 1). The boosting processingincludes the control of the rotation of the spindle motor 7 by the servosystem 50, the control of the movement of the head 8, the control of thepower of the semiconductor laser of the head 8, the focusing control ofthe optical system, the tracking control, and the like. In the boostingprocessing, both the clock reproduction permit signal 34 and the addressreproduction permit signal 36 are reset to “0”.

Once the head 8 is positioned above a predetermined track of the opticaldisk 1 a by tracking, the VFO region is detected in the manner describedabove (step 2). When the “1” level of the VFO detection pulse isdetected, the clock reproduction permit signal 34 is set at “1” (step3). Subsequently, the address reproduction permit signal 36 is set at“1” (step 4). After the lapse of a predetermined time period, theaddress reproduction permit signal 36 and the clock reproduction permitsignal 34 are reset to “0” again (step 5), and the sectorsynchronization pulse 31 is detected (step 6).

The sector synchronization pulse 31 becomes “1” when the addressdemodulation circuit 30 reads address information correctly. Insynchronization with this pulse signal, the address information 40output from the address demodulation circuit 30 is read, so as todetermine whether or not it indicates a target recording sector (step7). If the read address information 40 indicates the target recordingsector, the process proceeds to the control for recording/reproduction(step 8). If the read address information 40 does not indicate thetarget recording sector, the process proceeds to the seek control (step9).

If the address demodulation circuit 30 fails to read the addressinformation, the sector synchronization pulse 31 will not become “1” fora predetermined time period at step 6. In such a case, the processreturns to step 2 for the VFO detection.

With the process along the flow described above, the clock reproductionpermit signal 34 and the address reproduction permit signal 36 aregenerated at the timing as shown in FIG. 14. Thus, smooth reading ofaddress information is possible even in the state observed beforeaddress information is reproduced immediately after the switching-on ofthe device, where the time reference by the sector synchronization pulse31 has not yet been provided.

FIG. 16 is a flowchart showing an example of a process performed by thesystem control 18 for switching the processing mode between the initialmode and the normal mode. The initial mode as used herein corresponds tothe time period from the switching-on of the device or a track jump toperform a seek and the like until the address information is firstreproduced. The normal mode corresponds to the time period after apredetermined address information has been read until a next track jumpis generated.

Referring to FIG. 16, the processings from step 1 through step 9 are thesame as corresponding processings in FIG. 15. The description thereof istherefore omitted here.

As shown in FIG. 16, at step 10, whether the mode is the initial mode orthe normal mode is determined. When the address information has beencorrectly read and recording/reproduction at the target recording sectorhas been performed in the preceding processings, the mode is determinedto be the normal mode. The mode is determined to be the initial modeafter the boosting processing (step 1), after the reading of the addressinformation is unsuccessful at step 6, or after the address informationwhich has been successfully read is determined not to be the targetrecording sector at step 7 and the seek control is performed (step 9).

In the normal mode, the VFO detection processing (step 2) is notperformed, but the processings of steps 3, 4, and 5 are performed usingthe timing at which the sector synchronization pulse 31 becomes “1” asthe reference. In the initial mode, the VFO detection processing (step2) is first performed, followed by the processings of steps 3, 4, and 5using the timing at which the VFO detection pulse 26 becomes “1” as thereference.

With the above processings, address information can be read smoothlyafter the switching-on of the device or after a track jump, and, afterthe reproduction of the address information, the address information andthe data can be read in a more ensuring manner using the sectorsynchronization pulse 31 as the reference.

Thus, in the first example, the method for recording/reproducing dataon/from the optical disk 1 a having the signal format shown in FIGS. 5Band 5C by use of the optical disk device 100 having the blockconstruction shown in FIG. 10, especially, the method for readingaddress information, was described.

In the first example, the (2, 10) modulation code is used as themodulation code for the address information regions ID of the headerregion 2 and the data recording region 4. It will be appreciated,however, that the modulation code is not restricted to the above, andany type of run length limit code having a fixed maximum inversioninterval may be used. The pattern of the address mark AM may bedetermined so that the above conditions for the maximum inversioninterval T_(max) are satisfied.

In the first example, the information recorded on the VFO regions hasbeen described to be a pattern composed of sequential 4-bit longmarks/spaces shown in FIG. 6. It is appreciated, however, that thepattern for the VFO regions is not restricted to this pattern, and anypattern may be used in which the length of each mark or space is equalto or more than the minimum inversion interval T_(min) and less than themaximum inversion interval T_(max) of the modulation code (run lengthlimit code) used for the recording on the address information region ID.As described above, however, since a shorter mark/space pattern having alength closer to the minimum inversion interval T_(min) is morepreferable since the number of repetition periods per unit length islarger and thus a faster clock reproduction is obtained.

In this example, the patterns shown in FIGS. 7A to 7C, FIGS. 8A to 8D,and FIG. 9 were described as examples of the address marks AM. Thepatterns of the address marks AM are not restricted to these patterns.The detection of the address marks AM is possible if the patternincludes two repetitions of a pattern having a length of 3 or more bitsadded to the maximum inversion interval T_(max) of the modulation code(run length limit code) used for the recording of the addressinformation regions ID.

In this example, the header region 2 is composed of four addressregions. The header region 2 is not restricted to this construction. Forexample, the reproduction of address information is possible by theconstruction of the header region which includes only one addressregion. However, the reliability of the reading of the addressinformation can be improved by forming a plurality of address regions IDwhere substantially the same address information is stored. As describedabove, in consideration of the error rate for the address informationand the allowance of the number of unrecognizable recording sectors, itis preferable to form four or more address regions for one header region2. Furthermore, in view of the practical allowance and the maximumsecurement of the data recording regions 4, it is more preferable forthe header to include four address regions ID as described in the firstexample.

(EXAMPLE 2)

FIG. 17A is a view illustrating a format of a recording sector 51 of anoptical disk of the second example according to the present invention.As shown in FIG. 17A, the recording sector 51 starts with a headerregion 52 where addressing information for reading address informationis prerecorded. A gap region 53, a data recording region 54, a postamblePAO, and a buffer region 55 respectively follow the header region 52 inthis order.

The gap region 53 has no data recorded thereon, but is used for powercontrol of a semiconductor laser used for data recording/reproductionand the like, for example. The data recording region 54 is used torecord user data. Redundant data such as an error correction code isadded to the user data, to form digital data. The digital data ismodulated using a run length limit code generated by use of a statemachine. The modulated data is recorded on the data recording region 54using the mark length recording. This run length limit code is called astate modulation code. The postamble PAO follows the end of the datarecording region 54. The pattern of the postamble PAO is determinedbased on the modulation results of the data recording region 54. Thebuffer region 55 is provided to absorb a rotational shift of the opticaldisk and the like. In the header region 52, information may be recordedas pits in a concave and convex shape on the recording surface, or asmarks optically recorded in substantially the same manner as that usedin the recording on the data recording region.

As shown in FIG. 17B, the header region 52 is divided into four addressregions 56 a , 56 b, 56 c, and 56 d. Each of the address regionsincludes a VFO region, an address mark AM, an address information regionID, and a postamble PA. For example, the address region 56 a includes aVFO region VF01, an address mark AM, an address information region ID1,and a postamble PA1, while the address region 56 b includes a VFO regionVFO2, an address mark AM, an address information region ID2, and apostamble PA2. The address information regions ID1, ID2, ID3, and ID4will hereinafter be collectively referred to as the address informationregion ID. Also, the postambles PA1, PA2, PA3, and PA4 will hereinafterbe collectively referred to as the postamble PA.

In this example, as in the first example, no sector mark is recorded oneach header region 52, but the four address regions similar to oneanother, each composed of the VFO region, the address mark AM, theaddress information region ID, and the postamble PA, are recordedsequentially.

The VFO regions VFO1, VFO2, VFO3, and VFO4 are used so that an opticaldisk device can obtain clock reproduction from a reproduced signal. Asin the first example, each VFO region has a sequential pattern thatincludes marks and spaces of a fixed length (e.g., 4-bit length)appearing alternately, for example. The VFO regions may have the samelength or different lengths. For example, if the head VFO region VFO1 ismade longer than the other VFO regions, stable clock reproduction isobtained at the beginning of the header region 52.

Each address mark AM is provided so that the optical disk device canidentify the position of the subsequent address information region ID.For example, like the address mark AM used in the first example, apattern including two repetitions of a pattern having a length of 3 bitsadded to the maximum inversion interval T_(max) of the state modulationcode is recorded.

On the address information region ID, digital data composed of dataincluding address information such as the track number and the sectornumber with a predetermined error detection code added thereto arerecorded using the mark length recording, after the digital data aremodulated using the state modulation code.

FIGS. 18A to 18C are conceptual views for explaining the modulationmethod and the demodulation method of the state modulation code used inthis example. The state modulation code is a modulation code whichconverts an 8-bit binary data unit into a 16-bit code sequence. A 16-bitoutput code sequence Y_(t) for an 8-bit input data D_(t) at a time t isdetermined based on a state S_(t) at the time t. FIG. 18A shows anexemplary construction of a state modulation circuit 60. As shown inFIG. 18A, the state modulation circuit 60 includes a conversion table 56and a D flipflop 57. The data D_(t) and the state S_(t) at the time tare input into the conversion table 56, and the code sequence Y_(t) anda state S_(t+1) at a next time t+1 (hereinafter, referred to as a nextstate) are output therefrom. The next state S_(t+1) output from theconversion table 56 is input into the D flipflop 57 to be used for thenext modulation.

FIG. 18B shows part of the content of the conversion table 56. The stateS_(t) at the time t includes a total of four states from St=1 to 4, anddifferent code sequences Y_(t) are allocated to the respective states.The state S_(t) and the data D_(t) at the time t determine the nextstate S_(t+1). The 16-bit sequences allocated as the output codesequences Y_(t) in the table are all the run length limit codes wherethe zero run is limited to the range of 2 to 10. Moreover, the nextstate S_(t+1) has been determined so that the zero run is still limitedto the range of 2 to 10 when the sequences at the two sequential timesare connected.

Among the 16-bit sequences allocated in the table as the output codesequences Y_(t), those of which next state S_(t+1) is 1 or 2 aredetermined so that the last zero run thereof is 5 or less.

There is a case where the same output sequence Y_(t) is allocated todifferent input data units D_(t), like patterns p1 and p2 shown by theunderlines in the table. In such a case, the next states for theseoutput sequences are determined to be either state 2 or state 3 so as tobe different from each other. In this case, for example, the pattern p1has the next state 2, while the pattern p2 has the next state 3. Exceptfor such a case, no double allocation of the same output sequence Y_(t)will be found.

The code sequences Y_(t) allocated to state 2 and state 3 have thefollowing features. The output sequence Y_(t) allocated to state 2 has“0”s at the first and thirteenth bits from left. The output sequenceY_(t) allocated to state 3 has “1”s at either the first bit or thethirteenth bit from left.

In the demodulation of the state modulation code, the 16-bit codesequence Y_(t) must be converted into an 8-bit binary data unit. FIG.18C is a block diagram for explaining the construction of a demodulationcircuit 61. In the demodulation circuit 61, the 16-bit code sequenceY_(t) at a time t and a first bit Y_(t+1 1) and a thirteenth bitY_(t+1 13) of a code sequence Y_(t+1) at a next time t+1, i.e., a totalof 18 , bits, are input into an inverse conversion table 58. The outputfrom the inverse conversion table 58 at the time t is an 8-bit binarydata unit D_(t).

The inverse conversion table 58 shown in FIG. 18B basically correspondsto an inverse view of the conversion table 56. For patterns which havenot been allocated double among the code sequences Y_(t), the binarydata unit D_(t) as the demodulation result thereof is uniquelydetermined.

For a pattern which has been allocated double, like the pattern p1 andp2 in state 1 shown in FIG. 18B, the binary data unit D_(t) thereofcannot be uniquely determined. However, as described above, such adouble allocation of the same code sequence Y_(t) is limited to the casewhere the next state thereof is state 2 or state 3. Accordingly, byrecognizing the difference between the code sequences of state 2 andstate 3, the original binary data unit D_(t) can be uniquely determined.In other words, the binary data unit D_(t) is uniquely determined byobserving the first and thirteenth bits of the code sequence at the timet+1 which is the code sequence determined by the next state at the timet during the modulation.

In the address information region ID, data including the addressinformation modulated in the modulation method as described above isrecorded using the mark length recording.

The postamble PAO shown in FIG. 17A indicates the end of the datarecording region 54, and has a pattern determined based on the modulatedresults of the data recording region 54.

The postambles PA1, PA2, PA3, and PA4 shown in FIG. 17B indicate theends of the address regions 56 a to 56 d, respectively, and havepatterns determined based on the modulation results of the correspondingaddress information regions ID1, ID2, ID3, and ID4 recorded immediatelybefore the postambles.

FIGS. 19A and 19B show examples of patterns of the postambles. The nextstate shown in FIGS. 19A and 19B indicates the next state obtained whenthe immediately preceding data unit has been modulated. In other words,for the postamble PAO, it indicates the next state obtained when the enddata of the data recording region 54 has been modulated. For thepostambles PA1, PA2, PA3, and PA4, it indicates the next states obtainedwhen the end data of the address information regions ID1, ID2, ID3, andID4 have been modulated. In the case where the next state is state 1 orstate 2, a pattern p3 shown in FIG. 19A is selected as the postamble. Inthe case where the next state is state 3 or state 4, a pattern p4 shownin FIG. 19B is selected as the postamble. The selected postambles arerecorded using the mark length recording.

When the pattern p3 follows any of the code sequences where the nextstate is state 1 or state 2, the zero run is still limited to the rangeof 2 to 10 at the coupling portion. When the pattern p4 follows any ofthe code sequences where the next state is state 3 or state 4, the zerorun is still limited to the range of 2 to 10 at the coupling portion.Therefore, the run length limit will not be broken by adding thepostamble. The first and thirteenth bits of the pattern p3 are both “0”,while the first bit of the pattern p4 is “1”.

By using the patterns p3 and p4 as the postambles, patterns recorded atthe end of the data recording region 54 and the address informationregions ID1, ID2, ID3, and ID4 can be uniquely demodulated.

As another feature, the second, twelfth, and fourteenth bits of thepattern p3 which are bits adjacent to the specific bits for identifyingthe state (the first and thirteenth bits) are all “0”. This prevents thestate from being mistakenly modulated by recognizing the thirteenth bitas “1” due to a bit shift and the like.

(EXAMPLE 3)

FIG. 20A schematically illustrates an optical disk 201 aof the thirdexample according to the present invention. Referring to FIG. 20A, theoptical disk 201 ahas tracks 201 b formed on the surface thereof in aspiral shape. Each track 201 b is divided into recording sectors 201 cin accordance with a predetermined physical format. As shown in FIG.20A, the recording sectors 201 c are sequentially arranged in thecircumferential direction to form one track 201 b.

FIG. 20B illustrates a format of each recording sector 201 c of theoptical disk 201 a of the third example according to the presentinvention. Referring to FIG. 20B, the recording sector 201 c starts witha header region 202 where addressing information for reading addressinformation is prerecorded. A gap region 203, a data recording region204, and a buffer region 205 follow the header region 202 in this order.The gap region 203 has no data recorded thereon, but is used for powercontrol of a semiconductor laser used for data recording/reproductionand the like. The data recording region 204 is used to record user data.Redundant data such as an error correction code is added to the userdata, to form digital data. The digital data is modulated using a runlength limit code where the zero run is limited to the range of 2 to 10,i.e., a (2,10) modulation code. The modulated data is recorded on thedata recording region 204 using the mark length recording. The bufferregion 205 is provided to absorb a rotational shift of the optical diskand the like. In the header region 202, information may be recorded aspits in a concave and convex shape on the recording surface, or as marksoptically recorded in substantially the same manner as that used in therecording on the data recording region.

As shown in FIG. 20C, the header region 202 is divided into four addressregions 206 a, 206 b, 206 c, and 206 d. Each of the address regionsincludes a VFO region, an address mark AM, an address information regionID, and a postamble PA. For example, the address region 206 a includes aVFO region VFO1, an address mark AM, an address information region ID1,and a postamble PA1, while the address region 206 b,includes a VFOregion VFO2, an address mark AM, an address information region ID2, anda postamble PA2. The address information regions ID1, ID2, ID3, and ID4are hereinafter collectively referred to as the address informationregion ID. Also, the postambles PA1, PA2, PA3, and PA4 are hereinaftercollectively referred to as the postamble PA.

In this example, as in the above examples, no sector mark is recorded oneach header region 202, but the four address regions, each composed ofthe VFO region, the address mark AM, the address information region ID,and the postamble PA, are recorded sequentially.

The VFO regions VFO1, VFO2, VFO3, and VFO4 are used so that an opticaldisk device can obtain clock reproduction from a reproduced signal. Asin the first example, for example, each VFO region has such a sequentialpattern that includes marks and spaces of a fixed length (e.g., 4-bitlength) appearing alternately. The VFO regions may have the same lengthor different lengths. For example, if the head VFO region VFO1 is madelonger than the other VFO regions, stable clock reproduction is obtainedat the beginning of the header region 202.

Each address mark AM is provided so that the optical disk device canidentify the position of the subsequent address information region. Forexample, as in the address mark AM used in the first example, a patternincluding twice repetition of a pattern having a length of 3 bits addedto the maximum inversion interval T_(max) of the modulation code (runlength limit code) is recorded.

On the address information region ID, digital data composed of dataincluding address information such as the track number and the sectornumber with a predetermined error detection code added thereto arerecorded using the mark length recording, after the digital data ismodulated using the state modulation code.

FIG. 21A shows an arrangement of the address regions of the headerregion 202 recorded on the recording surface of the optical disk of thisexample. As shown in FIG. 21A, in the optical disk, information isrecorded on both groove tracks and land tracks. The reference numerals210 and 212 denote the groove tracks, while the reference numeral 211denotes the land track. Address regions 213 to 220 are formed so as tooverride the adjacent groove tracks and land tracks. The address regions213 and 217 correspond to the address region 206 a. The address regions214 and 218 correspond to the address region 206 b. The address regions215 and 219 correspond to the address region 206 c. The address regions216 and 220 correspond to the address region 206 d. The distance betweenthe center line of the land track and the center line of the groovetrack is a track pitch Tp. Each address region is displaced from thecenterline of the track by T_(p)/2 toward inside or outside of the disk.For example, the address regions 213 to 216 are alternately arranged onboth sides of the groove track 210 with respect to the centerlinethereof. The reference numeral 207 denotes a light spot. During thereproduction, address information is read from the address regions 213to 216 along the groove track 210, and from the address regions 217,214, 219, and 216 along the land track 211. By arranging the addressregions in the above manner, it is possible to read the addressinformation from both the land tracks and the groove tracks.

Hereinbelow, a method for forming a prototype for producing a stamperused for the fabrication of a disk substrate having convex-shaped groovetracks and the address regions as concave and convex shaped pitsdescribed above will be described. The tracks and the address regionsare formed by irradiating the rotating disk prototype with laser lightfor cutting. By continuous radiation of laser light, the groove trackhaving one continuous groove is formed. By intermittent ON/OFF radiationof laser light, portions irradiated with laser light are formed as marks(pit data) in the address regions. The other portions which have notbeen irradiated with the laser light are left as spaces (non-pit data).For example, a predetermined pattern as described in the above examplesis recorded by a combination of the marks and the spaces. In thisexample, the address regions are arranged to be displaced inside andoutside the center of the track (wobbling arrangement). Accordingly, theON/OFF radiation of laser light is performed by shifting the center ofthe laser light for cutting in the radial direction by a predeterminedamount T_(p)/2 for every address region. Incidentally, at the productionof the disk prototype, the cutting is performed from the surfaceopposite the surface which is to be the recording surface at thereproduction operation. Therefore, the concave and convex portions ofthe pits and the grooves at the production of the disk prototype arereverse to those as are viewed from the reproduction head at the readingoperation.

FIG. 21B shows another arrangement of the address regions of the headerregion 202 recorded on the recording surface of the optical disk of thisexample.

In the optical disk shown in FIG. 21B, information is recorded on bothgroove tracks and land tracks. The reference numerals 210 and 212 denotethe groove tracks, while the reference numeral 211 denotes the landtrack. Address regions 213 to 220 are formed so as to override theadjacent groove tracks and land tracks. The address regions 213 and 217correspond to the address region 206 a. The address regions 214 and 218correspond to the address region 206 b. The address regions 215 and 219correspond to the address region 206 c. The address regions 216 and 220correspond to the address region 206 d. The distance between thecenterline of the land track and the centerline of the groove track is atrack pitch Tp. The two preceding address regions (213, 214, 217, 218)are displaced outside the centerlines 230 of the groove tracks byT_(p)/2. The two subsequent address regions (215, 216, 219, 220) aredisplaced inside the centerlines 230 of the groove tracks by T_(p)/2.The reference numeral 207 denotes a light spot. During the reproduction,address information is read from the address regions 213 to 216 alongthe groove track 210, and from the address regions 217, 218, 215, and216 along the land track 211.

By arranging the address regions in the above manner, it is possible toread the address information from both the land tracks and the groovetracks.

Moreover, since every two address regions as a unit are alternatelydisplaced inside and outside of the disk, the number of times at whichthe center of the laser light for cutting is shifted in the radialdirection by T_(p)/2 during the production of the disk prototypereduces, compared with the arrangement shown in FIG. 21A, facilitatingthe cutting of the prototype of the optical disk.

During the production of the prototype of the optical disk, as shown inFIG. 21A (FIG. 21B), the groove 210 and the address regions 213, 214,215, and 216 along the groove are first formed. Thereafter, after onerotation of the disk prototype, the groove 212 and the address regions217, 218, 219, and 220 along the groove are formed. At this time, due toa variation in the rotational precision of the disk prototype and thelike, the position of the address region 213 and the position of theaddress region 217 which corresponds thereto along the radial directionof the optical disk do not necessarily match with each other in thecircumferential direction. If the ends of the address regions 213 and217 are displaced by ΔX as shown in FIG. 21A (FIG. 21B), the end of theaddress region 217 (218) and the beginning of the address region 214(215) overlap with each other by ΔX when data on the land track 211 isreproduced. This may results in failure to reproduce address informationcorrectly.

To overcome this problem, as shown in FIG. 21C, it is arranged so thatno mark is recorded but a space is provided at the end of each addressregion and furthermore a space (ΔX1) longer than the rotationalprecision (ΔX) at the cutting of the disk prototype is provided at thebeginning of the next address region.

For example, the rotational precision at the cutting of the diskprototype is about 20 ns/revolution when the number of revolutions ofthe disk prototype is 700 rpm. Accordingly, in the case of an opticaldisk having a diameter of 120 mm, the value of ΔX is about 0.1 μm atmaximum when converted into a length.

The operation in the above case will be described.

FIGS. 22A and 22B schematically illustrate the coupling portion of thetwo address regions 213 (214) and 214 (215). In the data sequences ofthe address regions shown in FIGS. 22A and 22B, the end (the finalpattern) of the address region 213 (214) includes a mark, and the headpattern of the subsequent address region 214 (215) also includes a mark.FIG. 22A shows an ideal mark shape expected for such a data arrangement.In other words, the mark at the end of the address region 213 (214) andthe mark at the beginning of the address region 214 (215) have apredetermined length and are formed at a center position of therespective address regions. In reality, however, when address pits areformed while shifting laser light for each address region in the cuttingprocess of the disk prototype, if the marks consecutively appear in thecoupling portion of the address region 213 (214) and the next addressregion 214 (215), the laser continues to emit laser light for cuttingwhile shifting in the radial direction. Accordingly, in reality, themark at the end of the address region 213 (214) and the mark at thebeginning of the address region 214 (215) are consecutively formed asshown in FIG. 22B, forming an incorrect mark overriding the two addressregions. As a result, correct data reproduction becomes difficult.

FIG. 23A and 23B illustrate the reading operation when a light spot 207reproduces data from the land track 211.

FIG. 23A illustrates the case where the mark arrangement in the couplingportion of two adjacent address regions is not specifically considered.As shown in FIG. 23A, when the adjacent address regions 214 (215) and217 (218) spatially overlap by a cutting precision ΔX, data read fromthe two address regions temporally overlap by an amount corresponding toΔX. While the end of the address region 217 (218) includes a space, thebeginning of the address region 214 (215) includes a mark. As shown inFIG. 23A, when the space at the end of the address region 217 (218) isoverlapped by the mark at the beginning of the address region 214 (215),the end of the address region 217 (218) is regarded as having the mark.This causes a data error at the address region 217 (218).

FIG. 23B illustrates a data arrangement according to the presentinvention for overcoming the above problem. As shown in FIG. 23B, spacesare arranged at the end and the beginning of the adjacent addressregions. With this arrangement, even if the space at the end of theaddress region 217 (218) is overlapped by the space at the beginning ofthe address region 214 (215), the overlapping portion is still a space,generating no data error on the address region 217 (218). This mayresult in failing to read correctly the length of the space at thebeginning of the address region 214 (215).

However, the beginning of each address region includes the VFO regionand, generally, it is not necessarily required to read all data on theVFO region. Moreover, no problem arises in the reading operation of theaddress region as far as the synchronization of the address region isrecovered by the address mark AM following the VFO region so that theaddress information can be correctly recognized.

Also, at the cutting of the disk prototype, a space is always arrangedbetween adjacent address regions to prevent marks from beingcontinuously formed. Accordingly, the continuous radiation of laserlight while shifting in the radial direction is prevented. Accordingly,the formation of a defect mark as shown in FIG. 22B is prevented.

Thus, by arranging spaces at the head and the end of each address regionas shown in FIG. 23B, the failure in mark formation at the cutting ofthe disk prototype and the erroneous data reading due to the overlap ofthe address regions at the data reproduction from the address regions inthe case of the wobbling arrangement of the address regions can beprevented.

Hereinbelow, the case of applying the mark arrangement of the postamblePA in this example to the data arrangement using the state modulatingcode described in Example 2 (FIGS. 18A and 18B) will be described. FIGS.24A to 24D illustrate exemplary mark arrangements of the postamble PA inthe case of using the state modulation code. In FIGS. 24A to 24D, thenext state indicates the next state obtained when the immediatelypreceding data has been modulated, in other words, the next stateobtained when the data at the end of the corresponding addressinformation region ID has been modulated.

FIG. 24A shows the case where the next state is either state 1 or state2 (see FIG. 18B) and the end of the address information region ID is amark 240. In this case, a pattern p5 as shown in FIG. 24A,{0010010010000000}, is selected and recorded using the mark lengthrecording. As described in Example 2, since the last zero run in thecode sequence of which next state is either state 1 or state 2 is 5 orless, when any of the code sequences of which next state is either state1 or state 2 is coupled with the pattern p5, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first andthirteenth bits of the pattern p5 are both “0”. Also, by selecting thepattern p5, the end of the postamble PA, i.e., the end of the addressregion is always a space.

Accordingly, since both the head and the end of each address region arespaces, the failure in mark formation at the cutting of the diskprototype and the erroneous data reading due to the overlap of addressregions at the data reproduction of the address regions in the case ofthe wobbling arrangement of the address regions may be prevented.

Moreover, by setting the pattern of the VFO region arranged at thebeginning of each address region at a sequential pattern signal startingwith {000100010001000 . . . }, the coupling portion of the adjacentaddress regions always includes a 11-bit long space which is the maximuminversion interval. This makes it possible to increase the time for themovement of a laser beam at the cutting while the limit of the zero runof the run length limit code is maintained.

As a further feature of the pattern p5, the second, twelfth, andfourteenth bits which are bits adjacent to the specific bits foridentifying the state (the first and thirteenth “0” bits) are all “0”.This prevents the state from being mistakenly modulated by recognizingthe thirteenth bit as “1” due to a bit shift and the like.

The pattern of the postamble PA is not limited to the pattern p5 shownin this example. Any pattern can be used as far as the number of zerosin the zero run satisfies the limit of the run length limit code usedfor the address information region ID, the state information is 1 or 2,the pattern is different from that of the address mark AM, and thepattern includes an odd number of “1”s.

FIG. 24B illustrates the case where the next state is either state 1 orstate 2 (see FIG. 18B) and the end of the address information region IDis a space. In this case, a pattern p6 as shown in FIG. 24B,{0000010010000000}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 1 or state 2 is coupled with the pattern p6, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first andthirteenth bits of the pattern p6 are both “0”. Also, by selecting thepattern p6, the end of the postamble PA, i.e., the end of the addressregion is a space. Accordingly, both the head and the end of eachaddress region are spaces. Therefore, the failure in mark formation atthe cutting of the disk prototype and the erroneous data reading due tothe overlap of address regions at the data reproduction of the addressregions in the case of the wobbling arrangement of the address regionsmay be prevented.

Moreover, by setting the pattern of the VFO region arranged at thebeginning of each address region at a sequential pattern signal startingwith {000100010001000 . . . }, the coupling portion of the adjacentaddress regions always includes a 11-bit long space which is the maximuminversion interval. This makes it possible to increase the time for themovement of a laser beam at the cutting while the limit of the zero runof the run length limit code is maintained.

As a further feature of the pattern p6, the second, twelfth, andfourteenth bits which are bits adjacent to the specific bits foridentifying the state (the first and thirteenth “0” bits) are all “0”.This prevents the state from being mistakenly modulated by mistakenlyrecognizing the thirteenth bit as “1” due to a bit shift and the like.

The pattern of the postamble PA is not limited to the pattern p6 shownin this example. Any pattern can be used as far as the number of zerosin the zero run satisfies the limit of the run length limit code usedfor the address information region ID, the state information is 1 or 2,the pattern is different from that of the address mark AM, and thepattern includes an even number of “1”s.

FIG. 24C shows the case where the next state is either state 3 or state4 (see FIG. 18B) and the end of the address information region ID is themark 240. In this case, a pattern p7 as shown in FIG. 24C,{1000010010000000}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 3 or state 4 is coupled with the pattern p7, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first bitof the pattern p7 is “1”. Also, by selecting the pattern p7, the end ofthe postamble PA, i.e., the end of the address region is always a space.Accordingly, both the head and the end of each address region arespaces.

Therefore, the failure in mark formation at the cutting of the diskprototype and the erroneous data reading due to the overlap of addressregions at the data reproduction of the address regions in the case ofthe wobbling arrangement of the address regions may be prevented.

Moreover, by setting the pattern of the VFO region arranged at thebeginning of each address region at a sequential pattern signal startingwith {000100010001000 . . . }, the coupling portion of the adjacentaddress regions always includes a 11-bit long space which is the maximuminversion interval. This makes it possible to increase the time for themovement of a laser beam at the cutting while the limit of the zero runof the run length limit code is maintained.

The pattern of the postamble PA is not limited to the pattern p7 shownin this example. Any pattern can be used as far as the number of zerosin the zero run satisfies the limit of the run length limit code usedfor the address information region ID, the state information is 3 or 4,the pattern is different from that of the address mark AM, and thepattern includes an odd number of “1”s.

FIG. 24D shows the case where the next state is either state 3 or state4 (see FIG. 18B) and the end of the address information region ID is aspace. In this case, a pattern p8 as shown in FIG. 24D,{1000000010000000}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 3 or state 4 is coupled with the pattern p8, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first bitof the pattern p8 is “1”. Also, by selecting the pattern p8, the end ofthe postamble PA, i.e., the end of the address region is always a space.Accordingly, both the head and the end of each address region arespaces. Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the data reproduction of the address regions in thecase of the wobbling arrangement of the address regions may beprevented.

Moreover, by setting the pattern of the VFO region arranged at thebeginning of each address region at a sequential pattern signal startingwith {000100010001000 . . . }, the coupling portion of the adjacentaddress regions always includes a 11-bit long space which is the maximuminversion interval. This makes it possible to increase the time for themovement of a laser beam at the cutting while the limit of the zero runof the run length limit code is maintained.

The pattern of the postamble PA is not limited to the pattern p8 shownin this example. Any pattern can be used as far as the number of zerosin the zero run satisfies the limit of the run length limit code usedfor the address information region ID, the state information is 3 or 4,the pattern is different from that of the address mark AM, and thepattern includes an even number of “1”s.

FIGS. 24E to 24H illustrate alternative examples of mark arrangement ofthe postamble PA in the case of using the state modulation code. InFIGS. 24E to 24H, the next state indicates the next state obtained whenthe immediately preceding data has been modulated, in other words, thenext state obtained when the data at the end of the correspondingaddress information region ID has been modulated.

FIG. 24E illustrates the case where the next state is either state 1 orstate 2 (see FIG. 18B) and the end of the address information region IDis the mark 240. In this case, a pattern p9 as shown in FIG. 24E,{0000010000010001}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 1 or state 2 is coupled with the pattern p9, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first andthirteenth bits of the pattern p9 are “0”. Also, by selecting thepattern p9, the end of the postamble PA, i.e., the end of the addressregion is a space.

Accordingly, both the head and the end of each address region arespaces. Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the data reproduction of the address regions in thecase of the wobbling arrangement of the address regions may beprevented.

Moreover, by setting the pattern of the VFO region arranged at thebeginning of each address region at a sequential pattern signal startingwith {000100010001000 . . . }, the 4-bit long mark at the end of thepostamble can be used as the VFO.

FIG. 24F illustrates the case where the next state is either state 1 orstate 2 (see FIG. 18B) and the end of the address information region IDis a space. In this case, a pattern p10 as shown in FIG. 24F,{0001000100010001}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 1 or state 2 is coupled with the pattern p10, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first andthirteenth bits of the pattern p1 are “0”.

Also, by selecting the pattern p10, the end of the postamble PA, i.e.,the end of the address region is a space.

Accordingly, both the head and the end of each address region arespaces. Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the data reproduction of the address regions in thecase of the wobbling arrangement of the address regions can beprevented.

Moreover, by setting the pattern of the VFO region arranged at thebeginning of each address region at a sequential pattern signal startingwith {000100010001000 . . . }, the 4-bit long mark at the end of thepostamble can be used as the VFO.

FIG. 24G illustrates the case where the next state is either state 3 orstate 4 (see FIG. 18B) and the end of the address information region IDis the mark 240. In this case, a pattern p11 as shown in FIG. 24G,{1000100100010001}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 3 or state 4 is coupled with the pattern p1, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first bitof the pattern p11 is “1”. Also, by selecting the pattern p11, the endof the postamble PA, i.e., the end of the address region is a space.

Accordingly, both the head and the end of each address region arespaces. Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the reproduction of the address regions in the caseof the wobbling arrangement of the address regions may be prevented.

Moreover, by setting the pattern of the VFO region arranged at thebeginning of each address region at a sequential pattern signal startingwith {000100010001000 . . . }, the 4-bit long mark at the end of thepostamble can be used as the VFO.

FIG. 24H illustrates the case where the next state is either state 3 orstate 4.(see FIG. 18B) and the end of the address information region IDis a space. In this case, a pattern p12 as shown in FIG. 24H,{1000010000010001}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 3 or state 4 is coupled with the pattern p12, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first bitof the pattern p12 is “1”. Also, by selecting the pattern p12, the endof the postamble PA, i.e., the end of the address region is a space.

Accordingly, both the head and the end of each address region arespaces. Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the reproduction of the address regions in the caseof the wobbling arrangement of the address regions can be prevented.

Moreover, by setting the pattern of the VFO region arranged at thebeginning of each address region at a sequential pattern signal startingwith {000100010001000 . . . }, the 4-bit long mark at the end of thepostamble can be used as the VFO.

Exemplary arrangements of the above-described patterns of the postamblePA will be described. As an example, postambles having the patterns p5to p8 shown in FIGS. 24A to 24D may be used as the postambles PA1, PA2,PA3, and PA4 shown in FIG. 20C. Alternatively, postambles having thepatterns p9 to p12 shown in FIGS. 24E to 24H may be used as thepostambles PA1, PA2, PA3, and PA4 shown in FIG. 20C.

Alternatively, the postambles having the patterns p5 to p8 shown inFIGS. 24A to 24D may be used as the postambles PA2 and PA4 shown in FIG.20C, while the postambles having the patterns p9 to p12 shown in FIGS.24E to 24H may be used as the postambles PA1 and PA3 shown in FIG. 20C.In this case, when the address regions on the disk are arranged as shownin FIG. 21B, the ends of the address regions 213 and 215 can be used asthe VFO regions between the address regions 213 and 214 and between theaddress regions 215 and 216, respectively, where the shifting of thelaser light for cutting is not required. Also, a 11-bit long space canbe secured between the address regions 214 and 215 where the shifting ofthe laser light for cutting is required. In this way, both the merits ofthe two types of patterns can be obtained. Moreover, in this case, bysetting the length of VFO1 and VFO3 larger than the length of VFO2 andVFO4, stable clock reproduction is obtained at the heading addressregions 213 and 215 in the wobbling arrangement. (Example 4)

FIG. 25A illustrates a format of a recording sector 61 of an opticaldisk of the fourth example according to the present invention. Therecording sector 61 starts with a header region 62 where addressinginformation for reading address information is prerecorded. A gap region63, a data recording region 64, a postamble 65, a guard data recordingregion 66, and a buffer region 67 follow the header region 62 in thisorder. The gap region 63 has no data recorded thereon, but is used forpower control of a semiconductor laser used for datarecording/reproduction and the like, for example. The data recordingregion 64 is used to store user data. Redundant data such as an errorcorrection code is added to the user data, to form digital data. Thedigital data is modulated using a predetermined run length limit code,and recorded on the data recording region 64 using the mark lengthrecording.

The postamble 65 indicates the end of the data recording region 64. Thepattern of the postamble 65 is determined based on the modulationresults of the data recording region 64. The postamble 65 includesinformation used at the modulation of data, like the stateidentification bit described in the second example. The guard datarecording region 66 is provided to suppress a degradation of therecording surface due to repeated recording of data on the samerecording sector, and includes dummy data which does not have specificinformation. The buffer region 67 is provided to absorb a rotationalshift of the optical disk and the like.

Data is recorded on the data recording region 64, the postamble 65, andthe guard data region 66 by irradiating the regions with a light spothaving a predetermined recording power to form optical marks on therecording surface. In general, the crystal structure of a thin film ofthe recording surface is changed into an amorphous state, to change thereflection characteristic of the mark portions. Thus, since a light spothaving a comparatively large power is formed for the data recording, therecording surface bears a heat load. This causes a degradation of therecording surface.

In particular, in each recording sector, the difference in the heat loadis generated at the boundary between a region where data has beenrecorded and a region where data has not been recorded. When datarecording is repeated, the material of the recording film shifts due tothe difference in the heat load. This may degrade the boundary region,thereby making it difficult to read data correctly. When such an opticaldisk that may be degraded at the recording surface due to repeatedrecording is used, important data should preferably be prevented frombeing recorded in the vicinity of the boundary where the difference inthe heat load may be generated. In this example, in order to overcomethe above problem, the guard data recording region 66 is provided. Theguard data recording region 66 includes dummy data, which providessubstantially the same level of heat load as that generated at therecording of data on the data recording region 64 or the postamble 65.In the data patterns written on the data recording region 64 and thepostamble 65, low-frequency components increase when the number of themarks or spaces appearing in the patterns exceeds majority. The increasein the low-frequency components is not preferable because it varies thenumber of reproduced signal components in a servo band, affecting theservo system. Thus, the number of the low-frequency components in thepatterns is desirably as small as possible. In many cases, therefore,the modulation is performed so that the total number of bits for marksand the total number of bits for spaces are as close as possible to eachother.

Accordingly, in the pattern of the dummy data recorded on the guard datarecording region 66, also, the total number of bits for marks ispreferably equal to the total number of bits for spaces. With thisarrangement, the heat load of the dummy data is in substantially thesame level as the heat load generated at the recording of data on thedata recording region 64 and the postamble 65.

For example, a pattern where a k-bit long mark and a k-bit long spaceare alternately repeated for an even number of times may be used,wherein k is a natural number satisfying T_(min) ≦k≦T_(max); T_(min) andT_(max) are the minimum and maximum inversion intervals, respectively,of the run length limit code.

The guard data recording region 66 preferably has a length of an integernumber of data bytes because such a length facilitates the processingsof the modulation circuit, the demodulation circuit, and the like.

FIG. 25B illustrates an example of a pattern recorded on the guard datarecording region 66 when such a modulation code that modulates one databyte into 16 bits (T_(min)=3, T_(max)=11) as was described above withreference to FIG. 18B is used. This pattern is composed of alternaterepetition of 4-bit long mark and space, and has a total length of 16×nbits (n is a natural number).

In FIG. 25B, the dummy data starts with a mark. It would be understoodthat the pattern may also start with a space depending on the pattern atthe end of the postamble 65.

Since the total number of bits for the marks is equal to the totalnumber of bits for the spaces, the heat load of the pattern shown inFIG. 25B is in substantially the same level as the heat load generatedat the recording of data on the data recording region 64 and thepostamble 65. Therefore, the degradation of the recording film due tothe difference in the heat load may be prevented.

Since the above pattern satisfies the conditions for the minimuminversion interval and the maximum inversion interval of the modulationcode (run length limit code), it will not affect the reproduction ofdata from the header region and the data region.

INDUSTRIAL APPLICABILITY

As described above, in an optical disk according to the presentinvention, address synchronous information and address informationmodulated using the run length limit code are recorded on the headerregion of each recording sector. The pattern of the address synchronoussignal includes two patterns having a length larger than the maximuminversion interval T_(max) of the run length limit code by 3 bits ormore. With this pattern, the reproduced signal of the addresssynchronous information is distinguished from the reproduced signal ofother information, thereby preventing easy occurrence of erroneousdetection of the address synchronous information. This makes it possibleto perform stable bit synchronization for reproduction of addressinformation using the address synchronization information without thenecessity of forming a sector mark in each recording sector.

The address synchronous information is recorded using first and secondpatterns which are different in either a physical shape or an opticalcharacteristic of the recording surface of the optical disk. Forexample, the first pattern is a convex portion (pit) formed physicallyon the recording surface thereof, and the second pattern is a concaveportion formed physically on the recording surface of the optical disk.Alternatively, the first pattern is a recording mark formed by changingthe reflection characteristic of the recording surface of the opticaldisk, and the second pattern is a space on the recording surface. Theaddress synchronous information includes one first pattern having alength of (T_(max)+3) bits or more and one second pattern having alength of (T_(max)+3) bits or more, so that the address synchronousinformation can be distinguished from other data modulated by the runlength limit code even when an error arises due to a bit shift and thelike.

By equalizing the total bit length of the first pattern included in theheader region and the total bit length of the second pattern includedtherein, the amount of low-frequency components contained in the patternmay be reduced. This will prevent the stability of the servo system frombeing lost during the data reproduction from the header region.

The header region includes four-time repetition of the addressinformation and the address synchronous information. This reduces thenumber of defective recording sectors where address information is notreadable in the optical disk with high recording density in an allowablerange. Thus, the present invention provides a high-quality optical disk.

In an optical disk according to the present invention, the header regionof each recording sector includes address information for identifyingthe position of the corresponding recording sector, address synchronousinformation for identifying the recording position of the addressinformation for bit synchronization, and clock synchronous informationfor reproducing the clock signal. The address information has beenmodulated using a run length limit code of a minimum inversion intervalof T_(max) bits and a maximum inversion interval of T_(max) bits(T_(max) and T_(min) are natural numbers satisfying T_(max)>T_(min)).The clock synchronous information is a sequential pattern of alternaterepetition of d-bit long mark and space (where d is a natural numbersatisfying T_(min)×3). The address synchronous information includes twopatterns of which inversion interval is (T_(max)+3) bits or more, sothat the reproduced signal of the address synchronous information isdistinguished from the reproduced signal of other information. Fasterclock reproduction is possible by reading the sequential pattern ofalternate repetition of the d-bit long mark and space. Also, stable bitsynchronization for reproducing the address information is possible byreading the address synchronous information.

In an optical disk according to the present invention, a pattern (sectormark) composed of a long mark for identifying the start of a recordingsector is not recorded at the beginning of the recording sector. Thisreduces the overhead amount of data as a format. At the same time, asdescribed above, both the detection of the beginning of the recordingsector and the clock reproduction can be performed using the clocksynchronous information.

In an optical disk according to the present invention, each recordingsector includes the header region and the postamble region following theend of the header region, and the postamble region includes a patterndetermined based on the modulation result of data of the header region.Accordingly, in the case where the data of the header region has beenmodulated using a modulation code for performing a conversion in a tablebased on a state, for example, the postamble can include thereininformation for state identification. This allows for efficientdemodulation of data in the header region.

In an optical disk according to the present invention, each recordingsector includes the header region, the data recording region, and thepostamble region following the end of the data recording region, whereinthe postamble region includes a pattern determined based on themodulation result of data on the data recording region. Accordingly, inthe case where the data of the data recording region has been modulatedusing a modulation code for performing a conversion in a table based ona state, for example, the postamble can include therein information forstate identification. This also allows for efficient demodulation ofdata in the data recording region.

The recording sector further includes the guard data recording regionfollowing the postamble region for recording dummy data. The guard datarecording region includes a pattern of alternate repetition of a k-bitlong optical mark and a k-bit long optical space, wherein k is a naturalnumber satisfying T_(min)≦k≦T_(max). This arrangement of the guard dataregion prevents the recording surface from being degraded due torepeated recording, as well as preventing the reliability of recordeddata from being lost.

In an optical disk according to the present invention, each recordingsector includes the header region, and the header region includes theaddress region having the postamble region at the end of the addressregion, and the postamble region has a pattern which ends with non-pitdata or a space. The header region includes a plurality of addressregions, and the VFO region at the beginning of each address region hasa pattern which starts with non-pit data or a space. Alternatively,non-pit data or a space having a length of T_(max) bits is providedbetween the address regions. With the above arrangement, in the case ofrecording the address regions in the middle of the land tracks and thegroove tracks, the formation of marks in the optical disk fabricationprocess is facilitated, and moreover erroneous reading of informationfrom the address regions may be prevented.

An optical disk device according to the present invention includes:means for reading a reproduced signal from the optical disk; addressreproduction means for obtaining the address information from thereproduced signal; detection means for detecting the sequential patternof the clock synchronous information from the reproduced signal tooutput a detection signal; and address reproduction permit means forpermitting the address reproduction means to perform a read operation ofthe address information based on the detection signal. With thisconstruction, stable and efficient reproduction of address informationis possible for an optical disk which does not include a sector mark (apattern composed of a long mark for identifying the start of a recordingsector) at the beginning of each recording sector, by detecting thesequential pattern of the clock synchronous information. Theconventional optical disk includes both a sector mark and clocksynchronous information on the header region. According to the presentinvention, since no sector mark is required, the date recording regioncan be increased.

An optical disk device according to the present invention includes:clock generation means for generating a clock signal from the reproducedsignal; and clock reproduction permit signal for permitting the clockgeneration means to perform an operation of generating the clock signalbased on the detection signal of the sequential pattern of the clocksynchronous information.

With this construction, stable and efficient reproduction of the clocksignal is possible for an optical disk which does not include a sectormark at the beginning of each recording sector, by detecting thesequential pattern of the clock synchronous information.

A reproduction method for an optical disk according to the presentinvention includes the steps of: retrieving a reproduced signal from theoptical disk; detecting the sequential pattern of the clock synchronousinformation from the reproduced signal; permitting reading of theaddress information if the sequential pattern is detected; reading theaddress information from the reproduced signal in response to thepermission; and terminating the step of reading the address informationin a predetermined time period after the permission to return to thestep of detecting the sequential pattern. With this method, stablereading of the address information at the switching-on of the device orimmediately after a track jump is possible for an optical disk having nosector mark but having clock synchronous information of a predeterminedsequential pattern.

A reproduction method for an optical disk according to the presentinvention includes the steps of: retrieving a reproduced signal from theoptical disk; detecting the sequential pattern of the clock synchronousinformation from the reproduced signal; permitting reproduction of aclock signal if the sequential pattern is detected; and reproducing theclock signal from the reproduced signal in response to the permission.With this method, stable reproduction of the clock signal at theswitching-on of the device or immediately after a track jump is possiblefor an optical disk having no sector mark for identifying the start ofthe recording sector, but having clock synchronous information of apredetermined sequential pattern.

A reproduction method for an optical disk includes the steps of:retrieving a reproduced signal from the optical disk; determining areproduction mode whether the reproduction mode is an initial modeduring a time period from the switching-on of the device or a track jumpuntil the address information is first read from the reproduced signalor a normal mode during a time period from the reading of the addressinformation until a next track jump is generated; detecting thesequential pattern of the clock synchronous information from thereproduced signal; permitting reading of the address information if thesequential pattern is detected in the initial mode as a first permittingstep; reading the address information from the reproduced signal inresponse to the permission; generating a sector pulse if the addressinformation is correctly read; permitting reading of the addressinformation from the reproduced signal based on the sector pulse in thenormal mode as a second permitting step; and terminating the reading ofthe address information to return to the step of determining areproduction mode if the address information fails to be read within apredetermined time period after either the first or second permissionstep. With this method, the processing after the switching-on of thedevice or a track jump until the address information is first reproducedand the processing at the normal data reproduction can be switchedtherebetween. Thus, efficient and reliable reading of the addressinformation of each recording sector is possible.

By combining the optical disk according to the present invention withthe optical disk device according to the present invention, or bycombining the optical disk of the present invention with the opticaldisk reproduction method, further stable and efficient reading of theaddress information is possible even in the case where the recordingdensity of the optical disk is improved by the technique such as themark length recording and the land/groove recording.

What is claimed is:
 1. An optical disk comprising a plurality of trackseach divided into a plurality of recording sectors, wherein: each of theplurality of recording sectors includes a header region, the headerregion includes a plurality of address regions, and each of the addressregions includes an address information region and a postamble regionwhich is provided following the address information region; addressinformation for identifying a position of a corresponding one of therecording sectors is recorded in the address information region, theaddress information being information which is obtained by modulatingeach data of a plurality of data based on a corresponding one of aplurality of states; information indicating a next state, to which astate which has been used to modulate a last one of the plurality ofdata is to transition, is recorded in the postamble region; theinformation indicating the next state includes a specific bit having apredetermined value; at least one bit of bits which are adjacent to thespecific bit has a value which is identical to the predetermined valueof the specific bit; and non-pit data or a space is located at an end ofthe postamble region.
 2. An optical disk according to claim 1, whereinan error detection code of the address information is recorded in theaddress information region.